1. Technical Field
The present invention relates to an image-capturing apparatus such as a digital camera or the like, and more particularly to an image-capturing apparatus having a plurality of optical systems for capturing an image of a scene.
2. Related Art
Many current digital cameras have a zoom lens and a single image sensor and capture a still image and a motion picture. The thus-captured image is digitally processed to thus create a digital image file, and the thus-created film is stored in memory in the digital camera. The digital image file is then transferred to a computer to be displayed thereon or to a printer to be printed thereby.
Desired specifications of a digital camera include compactness and a wide range of an optical zoom. The user prefers a zoom range which is wider than a limited zoom range. However, when the digital camera is provided with a lens of wide zoom range without sacrificing the quality of a captured image, the digital camera becomes bulky. A camera, as in the case of a single lens reflex camera which enables replacement of large lenses, enables use of a plurality of replacement lenses; e.g., a 28 mm to 70 mm zoom lens and a 70 mm to 210 mm zoom lens. However, a compact digital camera does not enable replacement of lenses.
Some digital cameras use a single lens and a plurality of image sensors for the purpose of generating a single color image. Light from a subject is split into a plurality of colors by means of a prism beam splitter. A plurality of monochrome image sensors are used for capturing R, G, B color images.
A stereoscopic-film camera and a stereoscopic digital camera have hitherto been known. Each of these cameras has two lenses of identical focal length which are horizontally spaced apart from each other. Images—which differ slightly from each other in terms of a scene—are formed in two frames of a film or on two image sensors. The two images form a so-called stereoscopic pair. The two lenses are designed so as to exhibit the same scaling factor; and are concurrently used to thus create an image for the left eye and another image for the right eye on an image sensor in order to achieve a stereoscopic effect.
In order to achieve a wide zoom range without replacement of a lens, the compact digital camera is equipped with a plurality of lenses having different focal lengths. Selection of a lens is performed depending on a zoom position. When a camera is equipped with two lenses of different focal lengths, the method of setting focal lengths of the two lenses and the method of switching between the two lenses become important. The reason for this is that the digital camera enables performance of an electronic zooming function of electronically zooming in with respect to digital image data as well as an optical zooming function.
Japanese Patent Laid-Open Publication No. Hei 10-42183 describes a camera having a single lens and a single image sensor, wherein an angle of view is determined by means of driving an electronic zoom and an optical zoom, and the proportion of the optical zoom is increased while the angle of view is maintained.
Japanese Patent Laid-Open Publication No. 2003-283910 describes a camera having an optical finder and an electronic finder, wherein, when switching between the optical finder and the electronic finder is effected as required; namely, when the electronic finder is switched to the optical finder, a lens of the optical finder system is actuated in synchronism with an image-capturing lens in such a way that the angle of view of the lens of the optical finder coincides with the angle of view of the image-capturing lens.
The respective related-art techniques relate to the cameras, each of which has a single lens and a single image sensor. None of these cameras are a camera system having a plurality of optical systems for capturing a scene. Consequently, as a matter of course, the method of switching among the plurality of optical systems is not disclosed.
A digital camera is assumed to have a fixed focal-length lens and a zoom lens, as two lenses. Switching between the two lenses is assumed to be performed as follows. Specifically, a focal length gap between the focal length of the fixed focal-length lens and the minimum focal length of the zoom lens is interpolated by electronic zooming of a digital image captured by the fixed focal-length lens. The camera is equipped with zoom setting means (a zoom button) used for setting a zoom position. The user sets the zoom setting means to a wide position or a telephotography position, to thereby be able to capture an image at a desired zoom position. When the user has set the zoom setting means, which is provided in the camera, to the “telephotography” position, the digital image captured by the fixed focal-distance lens is electronically zoomed in. At a point in time when the telephotography end of the electronic zoom has been attained, the lens is switched to a zoom lens. Subsequently, an optical zoom is performed by means of the zoom lens. When the user has set the zoom setting means to the “wide” position by means of actuating the zoom setting means, the digital image acquired by the zoom lens is optically zoomed out. At a point in time when the minimum focal length of the zoom lens has been attained, switching is effected to en electronic zoom of the fixed focal-length lens, and subsequently the fixed focal-length lens is zoomed out.
Additionally, another digital camera is assumed to have zoom lenses as two lenses, and switching between the two lenses is assumed to be performed as follows. Specifically, an image-capturing optical system having a zoom lens of relatively-wide angle of view is taken as a first image-capturing optical system, and another image-capturing optical system having a zoom lens of relatively-narrow angle of view is taken as a second image-capturing optical system. In an initial state where power is active, both the first image-capturing optical system and the second image-capturing optical system are situated at the wide position. When the user sets the zoom setting means to the “telephotography” position, the first image-capturing optical system is actuated from the wide position toward the telephotography position, to thus perform zooming-in action. Upon arrival at the telephotography position, the first image-capturing optical system is switched to the second image-capturing optical system. Subsequently, the second image-capturing optical system is actuated from the wide position to the telephotography position, to thus perform zoom-in action. When the user has set the zoom operation means to the “wide” position by means of actuating the same, the second image-capturing optical system is actuated from the telephotography position to the wide position, to thus effect zoom-out action. Upon arrival at the wide position, the second image-capturing optical system is switched to the first image-capturing optical system. Subsequently, the first image-capturing optical system is actuated from the telephotography position to the wide position, to thus effect zoom-out action.
However, in the configuration where the first and second image-capturing optical systems are sequentially actuated from the wide position to the telephotography position, consumption of a certain period of time is required before the system arrives at the telephotography position; namely, the second image-capturing optical system arrives at the telephotography position. This may result in a case where the chance to activate a shutter is lost. There may also be a case where some users desire to move the second image-capturing optical system to the telephotography position immediately after power-on. Such a user's demand cannot be met by the above driving methods.
The present invention has been conceived in view of the above drawbacks, and provides an image-capturing apparatus having a plurality of optical systems, which can immediately provide a user's desired arbitrary angle of view and an angle of view frequently used by the user, such as a wide position or a telephotography position.